Asterisk + Skinny problems

I have a bunch of 7910’s that I managed to get registered with Asterisk:

managed5*CLI> skinny show devices
Name DeviceId IP TypeId R Model NL

test7 SEP0004C1878F8E 6 Y 7910 1

The problem is that the phone resets when I attempt to make a call or place a call to it.

If I pick up I have no dial tone and after 3-4 seconds the phone resets. When that happens, on Asterisk I see:

Attempting to Clear display on Skinny 500@test7
skinny_new: tmp->nativeformats=4 fmt=4
– Starting simple switch on ‘500@test7’

then the phone resets.

when I try to call it, it doesn’t ring, displays:

Found device: test7
– skinny_request(500@test7)
– Skinny cw: 0, dnd: 0, so: 0, sno: 0
skinny_new: tmp->nativeformats=4 fmt=4
– skinny_call(Skinny/500@test7-2)
Trying to send: ''
Displaying message ''
Displaying Prompt Status ‘Ring-In’
– Called 500@test7
– Skinny/500@test7-2 is ringing
skinny_hangup(Skinny/500@test7-2) on 500@test7

then the phone resets.

Registration messages are:

-- Starting Skinny session from

Device SEP0004C1878F8E is attempting to register
– Device ‘test7’ successfuly registered
Requesting capabilities
Received CapabilitiesRes
Buttontemplate requested
Sending 7910 template to 500@test7 (7910)
Recieved SoftKey Template Request
Received SoftKeySetReq
Received LineStateReq
Received Time/Date Request

what could be causing this ?